Data traffic may include several forwarding classes (emission priorities) that require different treatment on access to the data network. Data may also be assigned various levels of discard priority, sometimes designated by colour, for example green, yellow and red for high, medium and low priority, respectively. Both of these priorities need to be taken into account by data network entities involved in traffic management. Such entities include schedulers, data shapers, and policers. While schedulers and data shapers effect changes in the makeup of the data stream, policers monitor the data stream and identify violations of the constraints imposed on the data network, for example throughput. Because of this difference, policers provide an opportunity to ensure fairness with respect to network resource utilization.
Known policers have tried to use a serial or a hierarchical configuration to provide for both emission priority and discard priority. However in such configurations information can be lost between policers, thereby adversely affecting the policer's fairness. Hence, it would be desirable to provide a policer that maintains fairness.